Arctic Amplification

Arctic amplification is the faster warming of the Arctic compared with the global average. It arises because an initial temperature increase activates interacting positive feedbacks involving ice, snow, radiation, atmospheric stability and moisture, although some processes still oppose warming.

Ice, snow and ocean feedbacks

The most visible mechanism is the ice-albedo feedback, which links melting to greater absorption of solar energy.

• Warming reduces reflective sea ice and snow, exposing darker ocean or land that absorbs more sunlight and causes further warming.
• Open water stores additional heat during summer and releases it to the atmosphere in autumn and winter, while reduced sea-ice insulation allows more oceanic heat and moisture to escape.
• Earlier snowmelt and later snowfall extend the period during which land and ocean absorb solar radiation.

Temperature and radiation feedbacks

The Arctic atmosphere is often stably stratified, so warming remains concentrated near the surface. This produces a positive lapse-rate feedback, because limited warming aloft produces a smaller increase in outgoing longwave radiation than a more vertically uniform warming would.

• The basic Planck response, whereby a warmer Earth emits more infrared radiation, is a negative feedback; however, radiative damping is weaker at colder temperatures.
• Near-surface warming can strengthen temperature inversions and reinforce the surface-concentrated pattern of Arctic warming.

Moisture, clouds and heat transport

Additional heat and moisture imported from lower latitudes interact with local feedbacks and help sustain amplification, especially during the cold season.

• Higher atmospheric water vapour strengthens the greenhouse effect and increases downward longwave radiation.
• Clouds can warm the surface through longwave radiation and cool it by reflecting sunlight; their net feedback varies with season, cloud type and surface conditions.
• Poleward atmospheric and oceanic heat transport is not merely a local feedback, but it supplies energy that sea-ice, moisture and cloud processes can amplify.